(Not applicable)
1. Field of the Invention
The invention relates to electrical devices, and more particularly, to programmable connectors for selectively connecting multiple circuits.
2. Description of Related Art
Following manufacture, integrated circuits are typically powered up and run for a test period prior to shipping to customers in order to weed out those devices which fail prematurely. This process is called burn-in and is typically performed at elevated temperatures to help accelerate early failures, or xe2x80x9cinfant mortalities.xe2x80x9d The burn-in system typically consists of a burn-in tester which provides the electrical test signals to the packaged integrated circuit, referred to as the device under test (xe2x80x9cDUTxe2x80x9d), and an oven which provides the temperature acceleration. The DUT is loaded into a load board and placed in the oven. The load board is constructed using conventional printed circuit board techniques and materials. Electrical test signals are routed from the burn-in tester through the load board to the appropriate terminals or pins of the DUT package.
Conventionally, there is a wide variety of types of integrated circuit packages and number of pins on each package. In addition, for a given package type and pin count there is an infinite number of products which can be housed inside it. This means the routing of the electrical test signals to the pins of the package presents an extremely large number of combinations. Historically, a separate load board has been made for each product, wherein the traces on the load board which carry the electrical test signals are routed to the specific pins, or leads, of the product. This is a xe2x80x9chard wiredxe2x80x9d design which does not allow for changes in the routing of the electrical test signals either to accommodate different devices to be tested or to perform different tests on a device. If the product pinout changes, a new load board must be manufactured to be able to burn it in. Likewise, a new load board needs to be manufactured for every new product.
Load boards are expensive and their wiring to the burn-in tester is labor intensive and time-consuming. Part of the expense is due to a robustness requirement, whereby the load boards need to be able to operate at elevated temperatures (up to 350xc2x0 C. or more), provide little if any signal degradation and remain reliable for one to two years of continuous operation at the elevated temperatures. It therefore becomes important to minimize the need to replace load boards, to thereby reduce the production costs of integrated circuits. One way to minimize the need to replace load boards is to make them more versatile in their applicability.
Versatility can be achieved using a programmable connector which operates as a selectively configurable wiring interface between the load board on which the DUT is mounted and the burn-in tester. The programmable connector is thus designed to accommodate the electrical configuration of a variety of DUTs. Typically, the programmable connector employs a mechanical jumpering system, wherein transversely extending conductors are selectively connected to each other by placement of pins or other conducting bridges between them, as illustrated in FIG. 1. Conductors 12A and 12B are normally spaced apart and isolated from each other, for instance by an intervening insulating substrate 11 on which they are mounted in the programmable connector. One set of these conductors, 12A, is in electrical connection with the burn-in tester (not shown). The other set, 12B, is in electrical connection with the DUT (not shown). Programming the connector is effected using conducting pins 10 inserted in holes 16A formed on one side of the connector and holes 16B formed on the other side. The holes 16A and 16B are surrounded by conducting lands 18A and 18B, respectively, which are electrically contiguous with conductors 12A and 12B. When inserted in holes 16A and 16B, pins 10 make contact with the associated lands 18A and 18B and in this manner connect the corresponding connectors 12A and 12B. A plurality of pins 10 are used to make the connections required by the particular DUT and the test to be performed.
Other methods of selectively connecting a DUT to a burn-in testor are known. One known method uses an operationally similar scheme to that described above. Instead of holes, the connector is provided with arrays of header pins protruding outwardly from the programmable connector, each header pin being associated with a connector which is either in connection with the DUT or the burn-in testor. The header pins can be selectively shunted together to bridge the connection between the DUT and the burn-in tester in a selectively configurable manner.
The above prior art schemes suffer from several disadvantages, including those associated with size, cost, reliability and complexity. Because in both prior art systems discussed pins are used which protrude perpendicularly from the connector, the profile of the connector is increased in the pin direction, detracting from the stackability of the connectors when employed in sets of more than one. Additionally, especially with respect to the header pin system, the cost per device is high because of the increased complexity of the device. The use of pins to effect an essentially mechanical connection also introduces reliability concerns. Good electrical contact must be insured with the manual insertion of each pin or with the shunting of each pair of pins for proper operation. Finally, the complexity of the devices, especially the header type connector, increases the probability of failure of the device.
There therefore exists a long felt need to provide a simple programmable connector which is inexpensive to produce, has minimal profile and is readily stackable, and which is reliable and easy to operate.
In accordance with the present invention, a programmable connector is provided with programming regions which can be selectively activated using a conductive solution applied to the programming regions. The regions can be deactivated using a solvent or other material to remove the conductive solution.
Preferably, an array of programming regions is provided on a surface of the programmable connector, Each programming region is associated with a first conductor in connection with the burn-in tester and a second conductor in connection with the device under test. The first and second conductors have conductive portions which are electrically isolated from each other. A support region is disposed between the two portions, which support region serves to support the solution such that when the solution is applied to the programming region, it completes an electrical path between the conductive portions of the first and second conductors.
More preferably, the array of programming regions is in the form of an ordered matrix, with the pair of conductive portions of each programming portion being in the shape of two bars of an equal sign, making for easy visual recognition by the operator. Similarly, it is preferred that the conductive solution be visible, and be dispensed from a hand-held pen-type implement. Similarly, it is preferred that the solvent for removing the solution be dispensed from a hand-held pen-type xe2x80x9cerasingxe2x80x9d implement.